The prevalence of dementia due to Alzheimer?s Disease (AD) and Alzheimer?s Disease Related Disorders (ADRD) increases with advancing age. However, the ability to disambiguate cognitive decline due to typical aging from the earliest stages of AD and ADRD is challenging. In part, we are hampered by a lack of sensitive assessment tools across the adult lifespan that can be easily and widely deployed within diverse research settings and populations. We will address this limitation by developing, validating, norming, and disseminating a MobileToolbox of cognitive assessments that can be administered remotely via a smartphone in adults aged 20 to 85. We will accomplish this objective via the following aims: 1. Create the MobileToolbox Library of iOS and Android smart-phone based assessments. These will draw from our existing work with the NIH Toolbox, the International Cognitive Ability Resource (ICAR), ResearchKit, ResearchStack, the FaceName Test, and the Patient Reported Outcomes Measurement Information System (PROMIS). The library will be open source and available for integration of additional externally developed tests. 2. Develop and maintain the MobileToolbox Research Platform, a software platform to support clinical researchers, especially AD/ADRD investigators, and software developers in the dynamic, customizable integration of the Mobile Toolbox Library into research studies. This will be developed as an extension of the platform we built to support the 2015 launch of Apple?s ResearchKit. The Platform will support researchers to contribute or select assessments, to manage study and assessment protocols, and to receive, store, aggregate, analyze and share (as appropriate) data collected using iOS and/or Android smartphone devices. 3. Conduct psychometric activities to validate, norm and assess the reliability of the MobileToolbox in both the general population and various AD/ADRD research samples to create general population reference norms. The cognitive assessments will be validated against gold standard measures in healthy adults ages 20-85. The measures will then be normed and 3-month, 12-month and 24-month change scores calculated in an age stratified (20-85), iOS vs Android, national sample matching the 2020 US Census (N=6,800) for gender, race, ethnicity, SES and level of education. Additional validation and longitudinal evaluation will be conducted in healthy and clinical samples, including persons at risk for MCI or AD and ADRD cognitive impairments. Once developed and validated, the assessments within the MobileToolbox Research Platform can be used in treatment trials and ultimately within the clinical environment to treat and prevent Alzheimer?s Disease.